Ignition Only

[James Ballenger]

>The worst example of this is a turbo motor where you might be 
>running 17d of
>timing.   With too high of overlap cam this can be a major problem.

	Ummm, correct me if I'm wrong here but with a Turbo you want less
overlap.  The turbo is already forcing the mixture in, so you don't need
more time to pull it through?

	I have had the fortune of doing a lot of research recently for my
application (high revving 4 cylinder).  I was going to go with a Coil per
plug setup, but for ease I have settled on 2 GM waste spark coils.  They are
high energy and they only cost $20 each.  The catch is that you need
ignitors and computer to drive it (which is where the real money comes in).
DIS offers far better advance characteristics than distributors beacuse you
can customize your advance at any point in the rpm/load range as opposed to
the rpm/load setup of a distributor (mechanical & vacuum advance) where only
the location of the curve can be changed rather than the actual curve.  I
should point out that there is no distributor on my engine because it is too
heavy, too inaccurate, and inappropriate for 13,500 rpm.  

	However, for my 455 in my Pontiac engine, there would be absolutely
no reason to go with anything but a distributor/coil setup.  Especially with
the 4500 redline ;-).  

	It really depends on your setup and what you need.  I believe more
power can be obtained with DIS (coil per plug) vs a distributor setup.  The
real plus seems to be accuracy and customization that DIS can offer over a
distributor setup.  The question is really if you need that accuracy and
customization.  And yes, DIS offers a far greater ability to fire above
9,000 rpm.  *Most* distributor based systems start to lose their power at
9,000 rpm.  A good DIS setup will keep it going to about 15,000.

	Also, I can tell you that in my experience the waste spark does not
ignite the incoming mixture on a Turbo setup.  I will tell you if that is
the case or not on a radical cam/nat ass setup  by this spring.

Just my take,
James Ballenger
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